Photovoltaic structure for a roadway

ABSTRACT

A photovoltaic structure, or a photovoltaic structure for a roadway suitable for circulation of pedestrians and vehicles, including: at least one photovoltaic cell; and a non-opaque coating covering at least a front face of the photovoltaic cell and having an outer surface which is macrotextured and microtextured irregularly, with a mean texture depth MTD, measured according to the norm NF EN 13036-1, of between 0.2 mm and 3 mm, and a polishing resistance value PRV, according to the norm NF EN 13043, of at least PRV44, or PRV50, or PRV53.

The present invention relates to photovoltaic structures, intended inparticular to form a roadway suitable for pedestrian and vehiculartraffic and having in particular an outer surface that reproduces thetexture of a trafficable road surface dressing.

PRIOR ART

There is a need to use roads as a means of producing energy during theday, whether this is to supply buildings located in the vicinity(businesses, eco-districts, single-family houses, etc.) or to supply thepower grid or traffic control devices.

Owing to the extent of the surface area of the road network, this couldmake it possible to avoid fields of solar modules that use arable landfor energy production or to increase the surfaces that are currentlyusable such as roofs.

US 2005/0199282 A1 discloses a roadway that incorporates a photovoltaicstructure, comprising solar cells covered by a non-opaque surfacing thatmust withstand the weight of vehicles and provide a sufficientcoefficient of friction to allow the latter to travel without skidding.

As examples of surfacings, mention is made of materials such astransparent plastics surface-coated with an abrasion-resistant layer,tempered or annealed glass, a complex formed of 5 mm glass beads bondedby an epoxy resin onto annealed glass, with a preference for a complexformed of polycarbonate-backed acrylic.

The structure may have frictional elements at the surface that areintended to increase the coefficient of friction. These frictionalelements may be arranged in patterns such as long or short straight orcurved lines, circles or other geometrical figures.

The frictional elements may be formed by bars or spikes or by groovescut into the surface of the surfacing. The frictional elements, whenthey are added, may be made of stainless steel or of polycarbonate.

There is a need to further improve the photovoltaic structures intendedfor pedestrian or vehicular traffic.

SUMMARY

One subject of the invention is, according to a first of its aspects, aphotovoltaic structure (also referred to as complex) in particular for aroadway suitable for pedestrian and vehicular traffic, comprising:

-   -   at least one photovoltaic cell,    -   a non-opaque surfacing, covering at least the front face of said        photovoltaic cell and having an irregularly macrotextured and        microtextured outer surface with a mean texture depth MTD        measured according to the NF EN 13036-1 standard of between 0.2        mm and 3 mm and a PSV (polished stone value) value according to        the NF EN 13043 standard of at least PSV₄₄, better still PSV₅₀,        even better still PSV₅₃.

The term “irregularly” is understood to mean the fact that the reliefsgiving the macrotexture and the microtexture do not all have the sameshape or the same size. These reliefs may be obtained from texturingelements that do not have the same shape or the same size, beingnon-calibrated. The nature, the mean size, the mean aspect ratio and themean surface density of the texturing elements are specifically chosenso as to obtain the desired MTD and PSV values.

Unlike the uniformly textured structure presented in patent applicationUS 2005/0199282, a structure according to present invention has, at thesurface, an irregular, preferably random, dispersion of non-opaquerelief elements, of irregular and preferably random shape themselves,which approaches the surface appearance of a well-known surface dressingof the road industry. Furthermore it has both macroscopic-scale(macrotexture) and microscopic-scale (microtexture) topographiesfavorable to grip. Therefore, the particular surface characteristics ofthe present invention are selected to have favorable levels ofmacrotexture and of microtexture that meet specifications in terms ofMTD and PSV making the surfacing suitable for traffic.

Moreover, the present invention is preferably carried out usingtexturing elements such as glass grains which 1) replicate the textureof a road and provide measured grip properties that conform to thespecifications (BO [Official Bulletin] 2002-10: circular 2002-39 of 16May 2002 relating to the grip of new treads and the control of themacrotexture) and 2) can be applied, if this is desired, to constructionsites using public works machinery and techniques.

In one of its embodiments, the structure according to the presentinvention is a trafficable encapsulated photovoltaic unit.

The surfacing of a structure according to the invention makes itpossible, owing to the texture of its outer surface, to exhibit the gripsuitable for vehicular or pedestrian traffic, while effectivelyprotecting the photovoltaic cells positioned beneath this surfacing.

The invention makes it possible to not replace existing roadways; thestructure according to the invention may be compatible with most ofthese roadways without requiring excavations or the laying of thick andrigid photovoltaic blocks.

Furthermore, the invention makes it possible to use the know-how and thecustomary equipment that is used for manufacturing and maintaining roadsurfacings (finishing machines, spreading of binder and gravel, etc.).

Thus, the invention allows easy implantation of the photovoltaicstructure and, from an economic viewpoint, makes it possible tosignificantly reduce the laying and integration costs.

The grip characteristics of the surfacing according to the invention arepreferably close to those of conventional bituminous road surfacings andthe optical characteristics are compatible with obtaining a satisfactoryconversion efficiency of the solar energy into electrical energy.

The photovoltaic structure according to the invention may be producedaccording to two methods of implementation in particular.

According to a first method of implementation, the photovoltaic cellsare present within one or more modules covered by the non-opaque andtextured surfacing, the module(s) being inserted between this surfacingand the underlying road. In particular, the surfacing may, according tothis first method of implementation, also extend to the portion of theroad bearing the photovoltaic modules but not covered thereby, or elsebe limited to just the surface of the modules. The latter may beattached to the roadway by a tie layer.

According to a second method of implementation, the photovoltaic cellsare encapsulated in the non-opaque and textured surfacing, the surfacingthen extending preferably both on top of and underneath the photovoltaiccells. The surfacing may extend in contact with a tie layer deposited onthe road or directly in contact therewith. In particular, according tothis second method of implementation, the surfacing may be preassembledwith one or more photovoltaic modules, containing the photovoltaiccells, preferably using a mold.

Another subject of the invention is, according to another of itsaspects, independently of or in combination with the aforegoing, aphotovoltaic structure suitable for pedestrian and vehicular traffic,comprising at least one photovoltaic cell encapsulated in a non-opaquesurfacing, having an irregular, textured, outer surface that is suitablefor pedestrian and vehicular traffic.

Another subject of the invention is, according to another of itsaspects, independently of or in combination with the aforegoing, aphotovoltaic structure suitable for pedestrian and vehicular traffic,comprising at least one photovoltaic cell covered by a surfacing thathas an outer surface textured with an irregular relief, characterized byaggregates of irregular shape and/or by an imprint of aggregates ofirregular shape.

Another subject of the invention is, according to another of itsaspects, independently of or in combination with the aforegoing, aphotovoltaic structure suitable for pedestrian and vehicular traffic,comprising a surfacing that covers at least one photovoltaic cell, thissurfacing comprising a bituminous binder, a clear road binder ofsynthetic or plant origin, resins, adhesives or polymers, such as epoxyor polyurethane, and optionally texturing elements such as aggregates orgrains made of glass, that provide surface texturing.

Another subject of the invention is, according to another of itsaspects, independently of or in combination with the aforegoing, aphotovoltaic structure that makes it possible to produce a roadway, inthe form of a rolled-up flexible sheet, to be rolled out in order toform the wearing surface, comprising photovoltaic cells and a surfacingthat covers them, this surfacing having a textured outer surface.

According to all these subjects of the invention, the surfacing may beas defined subsequently, in the same way as the texturing elements used.

Another subject of the invention is a process for manufacturing aphotovoltaic structure, in particular according to the first aspect asdefined above, comprising the steps consisting in:

-   -   positioning texturing elements, preferably aggregates of        irregular, in particular random, shape, in the bottom of a mold,        the texturing elements preferably being arranged in a single        layer,    -   positioning one or more photovoltaic cells in the mold,    -   injecting or casting a non-opaque material in the fluid state        into or in the mold in order to cover the photovoltaic cell(s),        and retain the texturing elements. Preferably, the texturing        elements are positioned with a given surface density.

Another subject of the invention is a process for manufacturing aphotovoltaic structure, in particular according to the first aspect asdefined above, comprising the steps consisting in:

-   -   positioning one or more photovoltaic cells in a mold,    -   injecting or casting a non-opaque material in the fluid state        into or in the mold,    -   before curing said material, embedding texturing elements,        preferably aggregates of irregular, in particular random, shape,        in its surface, the texturing elements preferably being arranged        in a single layer.

Another subject of the invention is a process for manufacturing aphotovoltaic structure, in particular according to the first aspect asdefined above, comprising the steps consisting in:

-   -   positioning one or more photovoltaic cells in a mold, the bottom        of which is textured, preferably with a relief that reproduces        the imprint of aggregates of irregular, in particular random,        shape, and    -   injecting or casting a non-opaque material in the fluid state,        which is intended to cure, into or in the mold. Preferably, the        reliefs that reproduce the imprint of the texturing elements are        distributed with a given surface density.

Another subject of the invention is a process for manufacturing aphotovoltaic structure, in particular according to the first aspect asdefined above, comprising the steps consisting in:

-   -   positioning one or more photovoltaic cells in a mold,    -   depositing a transparent polymer film of given thickness on the        photovoltaic cell(s),    -   depositing texturing elements, preferably aggregates of        irregular, in particular random, shape, on its surface, the        texturing elements preferably being arranged in a single layer,    -   subjecting the assembly to a hot pressurized laminator, the heat        ensuring the softening of the film and enabling the aggregates        to be embedded therein. Preferably, the texturing elements are        positioned with a given surface density.

In all the processes involving texturing elements, the latter arepreferably trapped between one quarter and three quarters of theirheight, preferably at around mid-height. The production of a singlelayer is preferable for reasons of photovoltaic performance.

Thus, in a first embodiment, texturing elements such as transparentaggregates are spread to saturation, and ideally as a single layer, onthe bottom of a mold. Once the transparent material which will have beeninjected or molded therein attains its final mechanical properties, theaggregates will be set in the material and will provide surfacetexturing.

In a second embodiment, transparent aggregates are inserted in thesurface of the molded photovoltaic complex, ideally before the injectedor molded transparent material has completely cured.

In a third embodiment, one face of the casting or injection moldadvantageously reproduces the imprint of a texture valid for a roadapplication, in particular having the desired MTD and PSV values,defined above. The cast or injected transparent material then reproducessaid texture.

Surfacing

The surfacing according to the invention is advantageously produced soas to have technical characteristics suitable both for pedestrian andvehicular traffic but that also enable its use in the photovoltaicfield. In particular, these characteristics relate to the transparencyand the surface texturing of said surfacing.

Transparency

In order to guarantee the desired photovoltaic performance, thesurfacing is non-opaque. It advantageously has a degree of transparencyof between 50% and 95%.

In order to characterize the degree of transparency, a spectrophotometerequipped with an integrating sphere is used. This device makes itpossible to quantify the light which passes directly through the sampleand that which is scattered by the sample, for a range of wavelengthvalues, in steps of 5 nm for example, this range preferably lying aroundthe peak of efficiency of the photovoltaic cells, plus or minus 100 nm.

The degree of transparency is measured for the thickness of surfacingpassed through by the light incident upon the wearing surface, beforereaching the photovoltaic cells.

The surfacing to be characterized is used on a glass plate. This plateis first characterized in terms of transparency by using the samespectrophotometer. The measurement is carried out in accordance with theprotocol described above and the transparency values obtained aresubtracted from those of the glass plate.

In order to have a characterization of the optical efficiency of thestructure according to the invention, the transmission values areweighted by the spectral response (sensitivity depending on thewavelengths) of the photovoltaic cells, the sensitivities of which inthe blue (450-520 nm) and in the violet (380-450) may be differentdepending on the type of technology used. Since the maximum efficiencyof the current technologies is in the green around 600 nm, the surfacingis preferably produced so that in the range 500 to 700 nm, its degree oftransparency is greater than 50%.

Surface Texturing:

In order to guarantee the desired grip performance, the surfacingaccording to the invention is advantageously produced so as to have anouter surface which is both macrotextured and microtextured.

Macrotexture

The macrotexture of the surfacing characterizes the surfaceirregularities in the range 0.5 to 50 mm horizontally (according to theNF EN ISO 13473-1 standard); the macrotexture facilitates the drainageof the water at the surface of the structure according to the inventionand makes it possible to avoid loss of tire/roadway grip in rainyweather.

A macrotexture has a texture wavelength ranging from 50 mm to 0.5 mm anda microtexture has a texture wavelength of less than 0.5 mm.

The macrotexture preferably has an irregular relief, which isadvantageously obtained owing to a well-defined choice of texturingelements, with a size and a surface density that are specificallychosen, of irregular, in particular random, shape, such as aggregates,or being the imprint of texturing elements of irregular shape, inspiredby the surface topography of road surface dressings.

Furthermore, the outer surface of the coating has a macrotexture depthpreferably such that the mean texture depth MTD measured according tothe NF EN 13036-1 standard is at least 0.20 mm, and preferably 0.30 mm,and ideally 0.60 mm or more, preferably being between 0.2 mm and 3 mm.

Microtexture

The surface of the surfacing also has a microtexture, in order to ensuregood grip of the tires.

The microtexture characterizes the surface irregularities, thecharacteristic horizontal size of which is less than 0.5 mm, accordingto the NF EN ISO 13473-1 standard.

The grip of the surfacing of the invention with respect to traffic,which conveys the quality of the microtexture, must remain afterpolishing, and may be expressed:

-   -   in terms of coefficient of friction μ_(WS), measured with a        Wehner and Schulze machine. Such a machine firstly carries out        up to 180 000 polishing cycles on the surface to be measured        (disk with a diameter of 225 mm), obtained by three cones under        a mixture of water and silica. Secondly, the device accelerates        a head bearing three rubber-based pads having a size of 30        mm×14.5 mm each up to 3000 rpm, which corresponds to a        tangential speed of 100 km/h. Water at 10° C. is sprayed onto        the surface to be characterized until a theoretical water film        thickness of 0.5 mm is formed. At that moment, the pads are        applied to the surface to be measured with a pressure of 0.2        N·mm⁻², equivalent to a tire pressure of 2 bar. The coefficient        of friction μ_(WS) is calculated at the speed of 60 km/h, and        may be given in terms of polished stone value PSV;    -   in terms of Polished Stone Value (PSV), using a friction pad as        described in the NF EN 1097-8 standard. The surfacing according        to the invention advantageously has a PSV value according to the        NF EN 13043 standard of at least PSV₄₄, preferably PSV₅₀, and        ideally PSV₅₃.

Irregular Nature of the Texture

The coating according to the invention has an irregularly macrotexturedand also irregularly microtextured outer surface.

It should be understood that the relief of the macrotexture or of themicrotexture is not reproduced in an identical manner, due to the use oftexturing elements that do not have the same shape or the same size, andthat are not calibrated. The relief may have a random nature, both inits macrotexture and its microtexture. The texturing elements are forexample shards or grains of glass, as specified below.

DETAILED DESCRIPTION

The invention will be better understood on reading the followingdescription, of exemplary embodiments that are not limiting thereto, andon examining the appended drawing, in which:

FIG. 1 schematically represents, in cross section taken through thethickness, an example of a roadway equipped with a photovoltaicstructure according to the invention,

FIGS. 2 and 3 are views similar to FIG. 1, of the embodiment variants ofthe photovoltaic structure,

FIGS. 4A to 4E illustrate the production of a structure and the usethereof according to one exemplary embodiment of the invention, and

FIGS. 5A to 5E and 6A to 6D are views similar to FIGS. 4A to 4E, ofembodiment variants of the invention.

In the drawing, the relative proportions of the various constituentelements have not always been respected, for the sake of clarity.Likewise, the texturing elements have been represented veryschematically, in a reduced number, in order to simplify the drawing.The conventional electrical connection elements have not beenrepresented.

A first example of a photovoltaic structure 10 according to theinvention is represented in FIG. 1. The structure 10 comprises one ormore modules 11 containing photovoltaic cells and a transparentsurfacing 12 that covers this or these modules 11.

The surfacing 12 mechanically protects the photovoltaic cells whileallowing pedestrian and vehicular traffic and its transparency enablesproduction of electrical energy by the modules 11.

The structure 10 has an irregular, granular, outer surface 13,preferably having a random relief.

The surfacing 12 is for example formed, as illustrated, from a binder14, also referred to as a matrix, embedded in which are transparenttexturing elements 16, such as aggregates formed from glass shards orglass grains, giving the outer surface 13 its granular appearance. Thetexture of the surfacing may also be produced by structuring of thesurface, without inclusion of aggregates in the binder.

The terms “transparent”, “translucent” and “non-opaque” are consideredto be synonyms within the context of the present invention.

The texture of the surfacing 12 guarantees a road holding similar to“conventional” roads, preferably with MTD and PSV values as definedabove.

The photovoltaic modules 11 may be flexible or semi-rigid, or evenrigid.

A tie layer 17 may ensure the attachment of the module(s) 11 to the roadR, which may be new or existing.

The example from FIG. 1 corresponds to the first method ofimplementation of the invention, defined above, according to which thesurfacing 12 extends on top of the photovoltaic module(s) 11 and is notinserted between the latter and the underlying road. Other variants willbe described below.

Irrespective of the embodiments, the binder used preferably has a degreeof transparency ranging from 80% to 100%.

Preferably, the material of the surfacing is selected so that the latterremains transparent over time, which can be verified via aging tests ina climatic chamber, by following for example the NFT 30-049 standard.The surfacing will lose no more than 20% after 5 days of aging in theWOM (Weather O Meter) according to the NFT 30-049 standard andpreferably no more than 10% of its initial transparency.

The structure illustrated in FIG. 1 may be produced by spreading thebinder in the fluid state over the surface of the photovoltaic modules11, and before the binder cures, the texturing elements 16 (preferablyin the form of transparent aggregates of irregular shape) may be spreadto saturation over the surface.

The amount of binder may be realized according to the traditional roadknow-how in order to trap the inclusions formed by the texturingelements, preferably at around mid-height.

Exemplary Embodiments of the Surfacing

According to a first exemplary embodiment of the surfacing, the binderis of bituminous type as defined in the NF EN 12591 standard, clear,i.e. unpigmented, the penetration classes of which determined accordingto the EN 1426 method may be, without limitation, 160/220, 100/150,70/100, 50/70, 40/60, 35/50, 30/45 or 20/30 (in tenths of a millimeter).Mention will be made, for example, of the Bituclair binder sold byColas.

According to a second exemplary embodiment of the surfacing, the binderis a clear road binder of synthetic or plant origin, the penetrationclasses of which determined according to the EN 1426 method may be,without limitation, 160/220, 100/150, 70/100, 50/70, 40/60, 35/50, 30/45or 20/30 (in tenths of a millimeter). Mention will be made, for example,of the Végécol or Végéclair binders sold by Colas.

According to a third exemplary embodiment of the surfacing, the binderis of purely synthetic or plant origin nature, the binder preferablybeing of organic nature, preferably of polymeric nature. Mention will bemade, by way of example and without limitation, of an acrylic, epoxy orpolyurethane resin, such as the epoxide varnishes referred to as VernisD sold by Résipoly, or else a Sovermol polyurethane sold by BASF.

The binders used in the invention may comprise initiators or catalysts,in particular for accelerating the curing. They may also compriseadditives, thickeners, fluxes or others to facilitate the spreading andthe obtaining of a film-forming surface of controlled thickness.

The binders used have a good UV resistance (both in terms oftransparency and mechanical properties), water resistance, heatresistance, cold resistance and frost resistance, which can be verifiedin a climatic chamber, by following for example the NFT 30-049 standard,and also good adhesion to the texturing elements 16 and the surface ofthe photovoltaic modules 11. Furthermore, these binders advantageouslyhave a flexibility similar to the complex formed by the wearing surfaceof the existing road and photovoltaic modules, namely ideally an elasticmodulus of between 0.1 and 10 GPa.

The examples of surfacings given above apply for all structuresaccording to the invention.

Examples of Texturing Elements

The production of a single layer of texturing elements 16 is preferablefor reasons of photovoltaic performance, since the optical transmissiondrops with the thickness of material.

The choice of the nature, particle size, shape factor and surfacedensity of the texturing elements aims to obtain:

-   -   a good angularity, allowing good grip between the tires and the        roadway, under dry or wet conditions: the macrotexture thus        obtained enables the drainage of water under the tire, whereas        the microtexture contributes to the grip; a random texture        characterized by texturing elements of random shape or that        reproduces the relief of texturing elements of random shape is        advantageous from this point of view;    -   an abrasion resistance in order to retain over time the desired        road-holding quality; the use of mineral materials of great        hardness, as texturing elements, is advantageous from this point        of view;    -   a good surface finish in order to ensure correct adhesion to the        binder; the use of aggregates of irregular, in particular        random, shape may contribute to the good attachment of these        aggregates to the matrix;    -   a good transparency, in order to retain the photovoltaic        performance.

The texturing elements are advantageously transparent materials (glass,polycarbonate, etc.), preferably made of glass, shards or grains,preferably grains of glass (crushed recycled or new glass).

The size of these elements, differentiated using a screen, may bemonodisperse or polydisperse, and range from 0.1 to 10 mm, better stillfrom 0.4 to 4 mm, and more preferably have a size ranging from 0.9 to1.4 mm.

In order to obtain the desired level of macrotexture, the surfacedensity of these texturing elements at the surface of the surfacing ispreferably between 0.1 and 5 kg/m², and advantageously between 0.7 and1.5 kg/m².

The shape factor of these structuring elements, that is to say the ratiofor one element between its greater length and its smaller width, ispreferably less than or equal to 8 and preferably between 1 and 3.

The mean texture depth MTD of such elements preferably is close to 0.8mm and corresponds to the ideal threshold of 0.6 mm, whereas in terms ofgrip and resistance to polishing, after 180 000 polishing cycles in theWehner and Schultze machine, the texturing elements preferably have acoefficient of friction μ_(WS) of 0.4, exceeding the μ_(WS)=0.30threshold of a Polished Stone Value 50.

The examples of texturing elements above apply for all the embodiments.

The photovoltaic modules 11 may be thin, flexible or semi-rigid (forexample photovoltaic modules of the Unisolar brand) and may beadhesively bonded directly to the surface of a road made of bituminousmixes or made of cement concrete. The rear face of the modules 11 ispreferably sufficiently rigid and solid to protect the photovoltaiccells from any puncturing by the surface asperities of the existing road(for example by the tops of aggregates), while following the change inthe surface topography of the roads (for example following the formationof ruts or a crack). For example, the rear face of the modules 11 ischaracterized by a fluorinated resin such asethylene-tetrafluoroethylene, for example that sold under the nameTefzel by DuPont, preferably having a thickness of 0.2 to 5 mm.

The roadway may be new or existing, preferably being produced frombituminous mix formulations that are not very prone to rutting, so thatthe topography of the surface of the road only changes slightly asvehicles pass over it.

The adhesive bonding of the modules 11 to the surface of the road R iscarried out with the tie layer 17, which may be formed of specialindustrial adhesives, or else of a bituminous binder, optionallyreinforced by an addition of a polymer such as SBS, hot or as anemulsion.

In a first embodiment, the adhesive or the bituminous binder forming thetie layer 17 is directly spread on the surface of the road R, spread outas a thin layer, then the photovoltaic modules 11 are deposited thereonwhile the adhesive has not cured or while the bituminous binder is stillviscous and tacky.

In a second embodiment, the binder intended to form the tie layer 17 isdeposited in the factory on the lower face of the photovoltaic modules11, which face may be untreated or may have undergone a plasma or coronatreatment in order to promote a better adhesion to the binder; thecomplex thus obtained is then adhesively bonded to the road R by aslight reheating of the binder on the back of the modules 11. Thecomplex corresponding to this second embodiment may be laid on a new orexisting road.

With reference to FIG. 2, a photovoltaic structure 10 according to thesecond method of implementation of the invention defined above will nowbe described, in which the photovoltaic cell(s) 11 are encapsulated inthe surfacing 12. The latter may also be attached to the road R by a tielayer 17, in the manner of the examples described previously withreference to FIG. 1.

The encapsulation ensures the (mechanical, hygrometric, leaktightness,etc.) protection of the photovoltaic cells.

The encapsulation is preferably produced by pre-positioning thephotovoltaic cell(s) 11 within a mold as illustrated in FIG. 4A, 5A or6A, and described in detail below. Next, the structure 10 is removedfrom the mold and may be attached to the existing road R owing to thetie layer 17.

In order to produce the surface texture of the surfacing, in a firstembodiment, illustrated in FIGS. 4A to 4E, texturing elements 16 such astransparent aggregates are spread to saturation over the bottom of amold, preferably in the form of a single layer, in what will then be thewearing surface of the structure. A transparent binder 14 is theninjected or poured into the mold. Once this material has attained itsfinal hardness and mechanical properties, the aggregates are firmlyattached to the contents of the mold and provide the desired surfacetexturing.

In a second embodiment, illustrated in FIGS. 5A to 5E, the transparentbinder 14 is firstly injected or poured into the mold (FIG. 5B), thenthe texturing elements such as transparent aggregates are spread overthe free surface of the mold (FIG. 5C), while the injected or pouredmaterial has not attained its final properties and still behaves as aviscous fluid. The texturing elements may be sunk in the binder via amechanical stress or sink by means of their own weight; it is alsopossible to heat the texturing elements in order to melt the binder inthe immediate vicinity thereof. Once the binder 14 has attained itsfinal hardness and mechanical properties, the aggregates are firmlyattached to the contents of the mold and provide the desired surfacetexturing (FIG. 5D).

These first two embodiments use texturing elements 16 added to thebinder 14 in order to give the surfacing 12 the desired texture,preferably in the form of a single layer.

In a third embodiment, illustrated in FIG. 3 and in FIGS. 6A to 6D, thelower face 45 of the mold M is textured and the desired texture is givenby the shape of this lower face. This face of the mold may reproduce animprint of random, irregular road texture, for example that of a surfacedressing having good grip to tires. After removal from the mold, awearing surface is obtained with relief elements 36 that give thedesired macrotexture and microtexture.

In a fourth embodiment:

-   -   a transparent polymer film, of given thickness, is deposited on        the photovoltaic cell(s),    -   texturing elements, in particular aggregates of irregular,        better still random, shape, are deposited on its surface, the        texturing elements preferably being arranged in a single layer,        and these elements are subjected to a hot pressurized laminator.        The heat ensures the softening of the film and enables the        aggregates to be embedded therein.

As encapsulant can be used for carrying out the invention according tothe second method of implementation, use may be made of any transparentmaterial (degree of transparency between 80% and 100%) capable of beingpoured or injected into a mold, in which photovoltaic cells have beenpre-positioned.

The role of the binder is to mechanically protect the photovoltaiccells, to hold the optional texturing elements that will give thesurface its texture, and therefore to enable the desired roadholding,while being and remaining transparent over time (by satisfying theclimatic chamber aging test according to the NFT 30-049 standard forexample).

The binder may be the same as according to the first method ofimplementation of the invention (see the section “Exemplary embodimentsof the surfacing” above) and have the same characteristics.

Thus, according to a first example, the binder is of bituminous type asdefined in the NF EN 12591 standard, clear (unpigmented), thepenetration classes of which determined according to the EN 1426 methodmay be, without limitation, 160/220, 100/150, 70/100, 50/70, 40/60,35/50, 30/45 or 20/30 (in tenths of a millimeter). Mention will be made,for example, of the Bituclair binder sold by Colas.

According to a second example, the binder is a clear road binder ofsynthetic or plant origin, the penetration classes of which determinedaccording to the EN 1426 method may be, without limitation, 160/220,100/150, 70/100, 50/70, 40/60, 35/50, 30/45 or 20/30 (in tenths of amillimeter). Use may be made of the Végécol or Végéclair binders sold byColas.

According to a third example, the binder is of purely synthetic or plantorigin nature, preferably of organic nature, preferably of polymericnature. Mention will be made, by way of example and without limitation,of an acrylic, epoxy or polyurethane resin, such as the epoxidevarnishes referred to as Vernis D sold by Résipoly, or else a Sovermolpolyurethane sold by BASF.

The texturing elements may be the same as those listed in the section“Examples of texturing elements”. The choice of the nature and of theparticle size of these inclusions corresponds to the same criteria asthose defined above. By way of example, glass aggregates, having a sizeof between 0.9 and 1.4 mm, may be used as texturing elements incombination with polyurethane of Sovermol type as binder. The degree oftransparency of such a surfacing is between 60% and 95% at 600 nm andideally 95%. The PSV values are preferably at least PSV₄₄, better stillPSV₅₀, even better still PSV₅₃, and the mean texture depth MTD ispreferably between 0.2 and 3 mm.

As a function of the transparency and mechanical protection objectives,the thickness of the photovoltaic structure 10 according to theinvention ranges for example from 0.5 to 30 mm, ideally from 0.6 to 12mm. It is not necessary for the thicknesses of binder on top of andunderneath the photovoltaic modules or cells 11 to be identical.

The adhesive bonding of the photovoltaic structure according to thissecond method of implementation of the invention to the surface of theroad may be carried out with special industrial adhesives, or else witha bituminous binder, optionally reinforced by an addition of a polymersuch as SBS, hot or as an emulsion.

In a first embodiment, the binder is directly spread on the surface ofthe road, spread out as a thin layer, then the prefabricatedphotovoltaic structure is deposited thereon while the adhesive has notcured or while the bituminous binder is still viscous and tacky.

In a second embodiment, the binder is deposited in the factory on thelower face of the prefabricated photovoltaic structure, which face maybe untreated or may have been treated by plasma or corona effect inorder to promote a better adhesion to the binder; the photovoltaicstructure is then adhesively bonded to the road by a slight reheating ofthe binder on the back thereof.

The front face may be produced during the manufacture of thephotovoltaic structure in the factory.

The wearing surface may also be produced on the road construction site,after having spread the photovoltaic modules or cells over the firstbituminous layers.

A photovoltaic structure according to the invention may also be proposedin the form of a textured complex that can be rolled out having a largeradius of curvature, whether the upper face (after rolling out) isalready pretextured or whether a layer based on a transparent binderbearing texturing elements such as transparent aggregates is addedthereto. The complex may include flexible electrical paths andconnectors. Construction site machinery may be used to roll out thecomplex on an existing road.

In a third embodiment, the surfacing is advantageously produced byimpregnation using a roller. The photovoltaic structure is positioned onthe road to be covered, and a roller preimpregnated with binder, inparticular with resin, is passed over the structure in the style of anapplication of paint.

Roadway

Generally, the roadway may be new or existing, but preferably producedfrom bituminous mix formulations that are not very prone to rutting, sothat the topography of the surface of the road only changes slightly asvehicles pass over it. The roadway may be a road, a freeway, a sidewalk.

Use of the Electrical Energy Produced

The electrical energy produced by a photovoltaic structure according tothe invention may be used in various ways, for example in eco-districts,solar farms, powering public lighting, road signaling or rechargingelectrical vehicles, this list not being limiting.

The invention may also be used for any type of application where theconcept of grip is important or for esthetic reasons.

The expression “comprising a” should be understood as being synonymouswith “comprising at least one”.

The invention claimed is:
 1. A roadway comprising: (i) a road having asurface made of bituminous mixes or made of cement concrete, and (ii) aphotovoltaic structure comprising: (a) at least one photovoltaic moduleadhesively bonded directly to the surface of the road, and (b) anon-opaque surfacing comprising: (1) a non-opaque matrix covering the atleast one photovoltaic module, and (2) non-opaque texturing elementsembedded in the non-opaque matrix, wherein the non-opaque texturingelements form reliefs of different shapes and different sizes on anouter surface of the non-opaque surfacing, the reliefs giving anirregular macrotexture and an irregular microtexture to the outersurface, with a mean texture depth measured according to the NF EN13036-1 standard of between 0.2 mm and 3 mm and a polished stone value(PSV) of resistance to polishing according to the NF EN 13043 standardof at least PSV₄₄.
 2. The roadway as claimed in claim 1, the meantexture depth being at least 0.30 mm.
 3. The roadway as claimed in claim1, the non-opaque surfacing having a degree of transparency of greaterthan 50% in a range of 100 nm around a peak of efficiency of thephotovoltaic module.
 4. The roadway as claimed in claim 1, a texture ofthe outer surface being defined at least partially by the non-opaquematrix.
 5. The roadway as claimed in claim 1, the non-opaque matrixbeing selected from materials of synthetic or plant origin, bituminousbinders, clear road binders of synthetic or plant origin, and polymericbinders.
 6. The roadway as claimed in claim 1, a density of texturingelements at the outer surface of the non-opaque surfacing being between0.1 kg/m² and 5 kg/m².
 7. The roadway as claimed in claim 1, thetexturing elements having a shape factor of less than
 8. 8. The roadwayas claimed in claim 1, the texturing elements being arranged in a singlelayer.
 9. The roadway as claimed in claim 1, the texturing elementsbeing selected from aggregates of organic or mineral, transparent ortranslucent, materials.
 10. The roadway as claimed in claim 1, thetexturing elements having a size ranging from 0.1 mm to 10 mm.
 11. Aprocess for manufacturing a photovoltaic structure as defined in claim1, comprising: positioning texturing elements in a bottom of a mold;positioning one or more photovoltaic cells in the mold; and injecting orcasting a non-opaque material in the fluid state into or in the mold tocover the one or more photovoltaic cells, and to retain the texturingelements.
 12. A process for manufacturing a photovoltaic structure asdefined in claim 1, comprising: positioning one or more photovoltaiccells in a mold; injecting or casting a non-opaque material in fluidstate into or in the mold; and before curing the material, embeddingtexturing elements in its surface.
 13. A process for manufacturing aphotovoltaic structure as defined in claim 1, comprising: depositing atransparent polymer film on one or more photovoltaic cells; depositingtexturing elements on its surface; and subjecting the structure to a hotpressurized laminator, heat ensuring softening of the film and enablingaggregates to be embedded therein.
 14. The roadway as claimed in claim1, the roadway having a grip suitable for traffic on a pedestrian andvehicular roadway.
 15. The roadway as claimed in claim 1, the PSV valueof resistance being of at least PSV₅₀.
 16. The roadway as claimed inclaim 1, the mean texture depth being at least 0.6 mm.
 17. The roadwayas claimed in claim 1, the non-opaque surfacing having a degree oftransparency of greater than 50% in a range of 500 nm to 700 nm.
 18. Theroadway as claimed in claim 1, the non-opaque matrix being selected frommaterials of synthetic or plant origin, bituminous binders, having apenetration class according to the EN 1426 standard of 160/220, 100/150,70/100, 50/70, 40/60, 35/50, 30/45, or 20/30 (in tenths of mm), andclear road binders of synthetic or plant origin, having a penetrationclass according to the EN 1426 standard of 160/220, 100/150, 70/100,50/70, 40/60, 35/50, 30/45, or 20/30 (in tenths of mm), and polymericbinders.
 19. The roadway as claimed in claim 1, a texture of the outersurface being defined at least partially by non-opaque texturingelements of irregular shape.
 20. The roadway as claimed in claim 1, thetexturing elements being arranged in a single layer sunk tomid-thickness approximately in the matrix of the non-opaque surfacing.21. The roadway as claimed in claim 1, the texturing elements beingselected from aggregates of polycarbonate or of glass.
 22. The processaccording to claim 11, the texturing elements being aggregates ofirregular shape arranged in a single layer.
 23. The process according toclaim 12, the texturing elements being aggregates of irregular shapearranged in a single layer.
 24. A roadway for pedestrian and vehiculartraffic, comprising a photovoltaic structure comprising at least onephotovoltaic module covered by a non-opaque surfacing having an outersurface textured with non-opaque texturing elements embedded in anon-opaque matrix, wherein the non-opaque texturing elements formreliefs of different shapes and different sizes on an outer surface ofthe non-opaque surfacing, the photovoltaic module being adhesivelybonded directly to the surface of the roadway made of bituminous mixesor made of cement concrete.
 25. The roadway as claimed in claim 1, thephotovoltaic module comprising at least one photovoltaic cell, a rearface of the photovoltaic module being sufficiently rigid and solid toprotect the at least one photovoltaic cell from any puncturing bysurface asperities of the road.
 26. The roadway as claimed in claim 1, arear face of the photovoltaic module being defined by a fluorinatedresin layer.
 27. The roadway as claimed in claim 26, the fluorinatedresin layer having a thickness of 0.2 to 5 mm.
 28. The roadway asclaimed in claim 1, the photovoltaic structure comprising a tie layeradhesively bonding the photovoltaic module to the road.
 29. The roadwayas claimed in claim 1, the tie layer having been directly spread on thesurface of the road, spread out as a thin layer before the photovoltaicmodule having been deposited thereon while the tie layer has not curedor is still viscous and tacky.
 30. The roadway as claimed in claim 1,the texturing elements having a size in a range from 0.1 mm to 1.4 mm.31. The roadway as claimed in claim 1, wherein a thickness of thephotovoltaic structure is in a range from 0.5 to 30 mm.
 32. The roadwayas claimed in claim 1, wherein a thickness of the photovoltaic structureis in a range from 0.6 to 12 mm.
 33. The roadway as claimed in claim 1,wherein the photovoltaic module comprises at least one photovoltaic celland a layer of polymer beneath the photovoltaic cell, the layer ofpolymer defining a rear face of the photovoltaic module.
 34. The roadwayas claimed in claim 33, the layer of polymer being fluorinated.